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Berkeley's Polypore - Bondarzewia berkeleyi

Good afternoon friends and happy Labor Day. I hope you're keeping the labor to a minimum and the relaxation to a maximum. This week's mushroom is Bondarzewia berkeleyi, commonly known as Berkeley's polypore. This mushroom was pointed out to me by Walkingstick Joe on 8/31/2021 growing at the base of an oak (Quercus) by Triplets bridge. I've also added a picture of a different specimen, posing with the Audubon Field Guide to Mushrooms, that Ethan pointed out to me in the North Woods back in July.


B. berkeleyi fruits mid-summer through mid-fall, roughly July through October. It's found in Europe, Asia, Africa, Oceania, and most predominantly in eastern North America. It forms concentric white bands on the cap and does not stain when handled - unlike the similar Meripilus sumstinei (the black-staining polypore). B. berkeleyi has white spores which can be seen covering the mushroom and the base of the oak in the first picture. The gregarious fruiting body grows out of a sclerotium (plural = sclerotia) which is a dense ball of mycelium used for long-term nutrient storage and, arguably, the most elaborate of fungal structures.

B. berkeleyi can be both saprobic (consuming nutrients from dead organic material - in this case dead oak wood) and parasitic. In instances where it is parasitic it causes a butt rot, almost exclusively on oaks. A butt rot is the fungus consuming the heartwood (the dead, central wood) in the trunk of the tree where it touches the soil. One thing I like to reiterate when we talk about parasitic/pathogenic fungi is that they aren't "bad", in fact they're essential for nutrient cycling and the overall health of our park and planet. While it's easy to look at this in a vacuum, as the fungus perhaps shortening the life of the tree, that's not how nature works. When we zoom out, we see everything in this world is interconnected and dynamic. The fungus is helping free up carbon locked in the dead plant cells within the tree, which will support more subterranean microbes and fungi, and allow for a healthier soil. When this tree's day eventually comes; it's wood will feed trillions of organisms, the canopy opening will give an opportunity to the millions of seeds in the soil that are waiting for the sunlight they need to germinate, and the growth of those plants will subsequently attract new microbes and fungi in the soil.

Fun Facts

Off the bat it is one of the largest mushrooms in the world, and certainly the largest we have featured on Mushroom Monday. Under the right conditions the caps can grow up to 1 meter wide while weighing up to 50 pounds (including sclerotium). It is also reported to be edible when young, and at its most tender, but all I found online is that it tastes like shoe leather.

Another interesting note is that it is in the family Russulaceae, meaning it is closely related to Russula (like Russula mariae featured a few weeks ago) and Lactarius species - though sharing very little physical resemblance. Lastly, the genus "Bondarzewia" is named after Russian mycologist A.S. Bondarzew and the species "berkeleyi" is named after the founder of British mycology, Miles Joseph Berkeley.

We're cruising into beautiful fall weather now gang,



1) Kuo, M. (2004, November). Bondarzewia berkeleyi. Retrieved from the MushroomExpert.Com Web site:

3) Mccoy, Peter. Radical Mycology : A Treatise on Seeing & Working with Fungi. Portland, Oregon, Chthaeus Press, 2016. Page 22.


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